1. Field of the Invention
The invention generally relates to a coolant recovery and recycling apparatus. In one aspect, the invention relates to a helium recovery and recycling apparatus associated with a heat exchanger.
2. Description of the Related Art
In the production of optical fibers, a glass rod or a xe2x80x9cpre-formxe2x80x9d, which is especially made to manufacture optical fibers, is processed in an optical fiber drawing system. The optical fiber drawing system generally comprises a furnace, a heat exchanger, a coating applicator, a dryer or curing furnace, and a spool as illustrated in European Patent Application No. 0079188. Initially, the glass rod is melted in the furnace such that a small, semi-liquid fiber is produced. The semi-liquid fiber is then cooled and solidified while falling through the air and the heat exchanger. Thereafter, the cooled, solidified fiber can be coated in the coating applicator, dried in the curing furnace or dryer, and drawn with the spool.
The drawing rate of the optical fiber is generally dependent upon the cooling rate of the optical fiber in the heat exchanger. That is, the rate at which the fiber can be drawn increases as the rate at which the fiber can be cooled increases. To increase the cooling rate of the optical fiber, a direct heat exchange process is employed. In the direct heat exchange process, a coolant gas (e.g., helium, nitrogen, a helium-nitrogen mixture, a helium-air mixture, a helium-argon mixture, a helium-hydrogen mixture, a helium-inert gas mixture, and the like) is introduced into the heat exchanger where the coolant gas directly encounters and cools the semi-liquid fiber.
Typically, the heat exchanger comprises a passageway (e.g., generally of a cylindrical configuration) having end openings (e.g., a fiber inlet and a fiber outlet) for receiving and expelling the optical fiber, one or more coolant gas inlets for receiving the coolant gas, and one or more coolant gas outlets for discharging the coolant gas. The passageway generally extends from one end opening proximate a top of the heat exchanger to another end opening proximate a bottom of the heat exchanger. Thus, the passageway provides a corridor through which the optical fiber can pass. The coolant gas inlet (or inlets) can introduce coolant gas into the passageway while the coolant gas outlet (or outlets) can remove the coolant gas from the passageway. In a conventional system, a rate of flow of the coolant gas into the heat exchanger is manipulated and/or controlled with metering valves and flow meters.
If any of the spent coolant gas is recovered from the heat exchanger, typically proximate the outlet, the recovered coolant gas will typically be entrained with and/or carry impurities, debris, and the like (collectively xe2x80x9ccontaminantsxe2x80x9d). Typical contaminants include gases (e.g., nitrogen, oxygen, argon, and other gases present in the atmosphere), particulate substances (e.g., dust), and moisture. These contaminants can infiltrate the passageway, coolant gas inlet, and/or coolant gas outlet of the heat exchanger. The contaminants can collect and increase in concentration in the recovered coolant gas. The amount and/or concentration of contaminants in the recovered coolant gas can limit and/or restrict the amount of coolant gas that can be recycled and reused.
In order to reduce the amount and/or concentration of contaminants in the recovered coolant gas, a variety of solutions for decontaminating and/or purifying the coolant gas have been suggested. Coolant gas purification devices, systems, and/or methods are often employed. Such purification devices and/or methods are intended to remove some of the contaminants from the recovered coolant gas so that at least a portion of the recovered coolant gas can be recycled. However, the use of purification devices can represent a substantial expense in the optical fiber manufacturing process.
Unfortunately, without using a purification device, the amount of impurities contained within the recovered coolant gas can be substantial. As attempts are made to recycle more of the recovered coolant gas, the contaminant concentration within the recovered coolant gas can resultantly increase. Therefore, a diminishing amount of recovered coolant gas can be available for recycling.
Thus, an efficient and less complex apparatus and method for recovering and recycling coolant gas would be desirable.
In one aspect, the invention provides a method of recovering and recycling a coolant gas containing contaminants. The method comprises providing a heat exchanger and an analyzer, the heat exchanger and the analyzer in operational association. The coolant gas containing contaminants is recovered from the heat exchanger and an analysis portion of the recovered coolant gas is delivered to the analyzer. Thereafter, the analysis portion of the recovered coolant gas is analyzed with the analyzer to determine a condition of the recovered coolant gas. Then, based on the condition, a reclaimed portion of the recovered coolant gas is blended with a virgin coolant gas to produce a gaseous coolant blend having a predetermined contaminant concentration. The gaseous coolant blend is introduced into the heat exchanger such that at least a portion of the recovered coolant gas is recycled.
In one embodiment, a method of recovering and recycling a coolant gas containing contaminants is employed. The method comprises providing a heat exchanger and an analyzer, the heat exchanger and analyzer in operational association. The coolant gas containing contaminants is recovered from the heat exchanger and an analysis portion of the recovered coolant gas is delivered to the analyzer. Thereafter, the analysis portion of the recovered coolant gas is analyzed with the analyzer to determine a condition of the recovered coolant gas. Then, based on the condition, a reclaimed portion of the recovered coolant gas is blended with a virgin coolant gas to produce a gaseous coolant blend having a predetermined contaminant concentration. The gaseous coolant blend is introduced into the heat exchanger such that at least a portion of the reclaimed recovered coolant gas is recycled. In this embodiment, the reclaimed recovered coolant gas is recycled as opposed to the recovered coolant gas.
In another embodiment, a method of controlling a contaminant concentration in a gaseous coolant blend provided to a heat exchanger is taught. The method comprises providing the heat exchanger and an analyzer, the heat exchanger and the analyzer in operational association. A coolant gas containing contaminants is recovered from the heat exchanger and an analysis portion of the recovered coolant gas is delivered to the analyzer. Thereafter, the analysis portion of the recovered coolant gas is analyzed with the analyzer to determine the contaminant concentration within the recovered coolant gas. Then, based on the contaminant concentration, a reclaimed portion of the recovered coolant gas and a virgin coolant gas are blended to produce the gaseous coolant blend. The reclaimed portion of the recovered coolant gas is recycled by introducing the gaseous coolant blend into the heat exchanger such that the contaminant concentration in the gaseous coolant blend provided to the heat exchanger is controlled.
In a further aspect, the invention provides an apparatus for use with a heat exchanger. The apparatus comprises a coolant recovery section, an analysis section, and a coolant gas blending section. The coolant recovery section is for recovering a coolant gas containing contaminants from the heat exchanger. The analysis section is operable to monitor a condition of the recovered coolant gas. The coolant gas blending section, in operational association with the coolant gas recovery section and the analysis section, is operable to produce, based on the condition of the recovered coolant gas, a gaseous coolant blend having a predetermined contaminant concentration from a virgin coolant gas and a reclaimed portion of the recovered coolant gas.
In one embodiment, an apparatus for recovering a coolant gas containing contaminants from a heat exchanger and recycling at least a portion of the recovered coolant gas is disclosed. The apparatus comprises a pump operable to recover the coolant gas from the heat exchanger and to transport the recovered coolant gas through the apparatus and an analyzer operable to monitor a condition of the recovered coolant gas. The apparatus also comprises a first mass flow controller operable to reclaim a portion of the recovered coolant gas by delivering the reclaimed portion of the recovered coolant gas to a mixing point, a second mass flow controller operable to provide a virgin coolant gas to the mixing point, and a third mass flow controller operable to maintain a flow of the recovered coolant gas through the apparatus. As such, the apparatus is operable to produce, based on the condition of the recovered coolant gas, a gaseous coolant blend from the virgin coolant gas and the reclaimed portion of the recovered coolant gas. Thus, the gaseous coolant blend has a predetermined contaminant concentration when the gaseous coolant blend is introduced into the heat exchanger.
In yet another aspect, the invention provides a coolant gas recovery system that comprises a coolant gas for cooling a hot fiber, a heat exchanger, a pump for pumping and drawing the coolant gas through the system, an analyzer for monitoring an impurity concentration in the coolant gas, a first mass flow controller and a second mass flow controller for controlling the impurity concentration in the coolant gas based on the monitored impurity concentration, and a third mass flow controller for providing a seal to the heat exchanger using the coolant gas and for maintaining a constant flow of the coolant gas to ensure continuous operation of the pump.
The heat exchanger includes a fiber inlet, a fiber outlet, a passageway, one or more coolant gas inlets, and one or more coolant gas outlets. The fiber inlet is adapted to receive the hot fiber into the heat exchanger and the fiber outlet is adapted to expel the hot fiber from the heat exchanger. The passageway extends between the fiber inlet and fiber outlet and is adapted to pass therethrough the hot fiber. The coolant gas inlets are for introducing a coolant gas into the passageway and the coolant gas outlets are for removing the coolant gas from the passageway.